1. Field of the Invention
The use of 1-hydroxyethyl-2-fatty acid imidazolines as a detergent in combination with free water added to an organic drycleaning solvent yields greatly improved drycleaning results.
2. Description of the Prior Art
Recent years have seen a rapid growth in the use of various solvents, notably perchloroethylene, trichloroethylene and Stoddard solvent, for the drycleaning of synthetic and natural fiber materials on both a professional (retail outlet) and industrial (rental garments) level. However, while a number of advances have been made, certain problems still exist. Foremost among these problems is the inability of the organic solvents to remove water-soluble soils.
Basically, the types of soils present on any article to be cleaned fall into three categories, i.e., water-soluble, solvent-soluble and insoluble. Obviously, the removal of solvent-soluble soils present little difficulty and, in fact, is one of the chief advantages of the use of drycleaning, as opposed to "wet" cleaning, processes. Likewise, the removal of insoluble soils presents no greater problem in drycleaning than in wet cleaning operations since the method of removal of these soils is basically mechanical. The chief problem with drycleaning systems therefore has been in the removal of water-soluble soils from the articles to be cleaned. That these water-soluble soils cannot be effectively removed by the solvents used in drycleaning is obvious.
In the usual commercial practice of drycleaning articles of clothing, the soiled garments are agitated in a perforated cylinder to remove oil, grease stains and particles of soil. Small quantities of water and detergent are also added to the solvent to help remove water-soluble soil and provide detergency. According to known practice, the drycleaning solvent is repeatedly recirculated through a filter to remove the soil particles from the solvent. After this cleaning phase, the solvent is drained from the cylinder and the garments are extracted (spun) to remove the bulk of the solvent from the wet load. The residual solvent and moisture deposited in the clothes are then removed by drying.
This usual commercial practice is suitable for the average soiled domestic garment such as trousers or coats which generally never lost more than about one to two pounds of soil per 100 pounds of clothes cleaned. However, such practice is unsatisfactory when the soil load in dirty garments increases greatly, e.g., from about 10 to 50 times greater than that normally handled in drycleaning the average soiled domestic garments. These high-soil loads are often found in the industrial garment or fabric. Typically, industrial garments and fabrics such as wiper cloths can have more than 50 pounds of soil in a 100-pound load of dirty cloths. When these soiled industrial garments are agitated in the organic solvent which is then recirculated in the usual way through a filter to remove the soil particles suspended in the solvent, filtration problems are encountered. The soil load is so great that filter pressure raises at such a rate that usually only one to three loads can be processed before flow completely stops. This poor filtration or lack of filtration makes it virtually impossible to satisfactorily dryclean by this known practice.
The most common method perhaps for drycleaning highly soiled garments requires an initial degreasing cycle. In the degreasing cycle, the dirty garments are flushed with solvent in a batch operation to remove the major portion of the solvent-soluble soil. The solvent is then removed from the washing system by extraction (spun off) and sent to a still along with dissolved grease, suspended insoluble soil, etc. After degreasing, new solvent is brought into contact with the clothes in the washer and this solvent is repeatedly recirculated through a filter to remove supposedly insoluble soil that was not removed in the degreasing cycle. Then the washer is isolated from the filtration equipment and put back on a batch operation in which soap and water are added to remove the water-soluble soil and/or texturizers and sizes are added to improve the hand of the fibrous material.
In this last-mentioned method, the drycleaning technique is so completely unsatisfactory that the garments must often be washed after drycleaning to make them presentable to customers. Because degreasing solvent has essentially no ability to suspend insoluble soil, it will redeposit back into the garment almost immediately unless removed from the system. However, since the garments cannot be safely filtered in view of the soil load, redeposition of insoluble soil on the garment takes place before the solvent is removed, especially in this batch operation. Many dingy and dirty garments generally come out of this cleaning cycle because of these conditions. Moreover, when water-soluble soil is attempted to be removed from the garment as to the last laundering phase of this known method, this attempt not only fails to remove the water-soluble soil but also tends to degrade garments much faster than even the degreasing operation.
It has, therefore, become essential that a drycleaning technique be provided which offers a satisfactory solution to the problems encountered in the presently proposed methods of cleaning highly soiled garments of the industrial type. There is a need for a drycleaning process which not only adequately removes all major types of soil and prevents redeposition of that soil but also prevents degradation of the fabric or garment. This is especially true since newly developed synthetics and synthetic blends, particularly those treated with permanent press finishes, cannot satisfactorily be washed. Moreover, it is important that other properties be obtained in such a process which make the garments presentable in addition to being clean.